1. Field of the Invention
The present invention relates to an optical information recording medium such as optical disks of a phase changing type and a write-once type and a magnetooptic disk for performing land and groove recording operations. The present invention also relates to an optical information recording-regenerating apparatus such as an optical disk drive unit for operating an optical disk and recording and regenerating optical information.
2. Description of the Related Art
An optical disk drive unit for operating an optical information recording medium such as an optical disk and a magnetooptic disk generally uses a recording system for realizing a high density record. This recording system is constructed by a ZCAV (Zoned Constant Angular Velocity) system, a system for reducing a wavelength of a laser diode, a PWM (pit edge recording) system, a land-groove recording system, etc. In the land-groove recording system, data are recorded to both land and groove portions formed by tracks formed on the optical information recording medium (which is called an optical disk in the following description). Accordingly, a data recording density in the land-groove recording system can be doubled in comparison with a general recording system in which data are recorded to only the land or groove portion.
The land-groove recording system in the above high density recording systems particularly has a problem about an error in detection of ID (identification) information and information data by crosstalk between the land and groove portions adjacent to each other. FIG. 1 shows an example for canceling such crosstalk in the land-groove recording system. This example is disclosed as "High Track Density Magneto-optical recording Using a Crosstalk Canceler" in Optical Data Strage '90. In FIG. 1, a land portion 2 and a groove portion 3 are alternately arranged on a face of a magnetooptic disk 1. Recording pits 4 are formed in both regions for the land portion 2 and the groove portion 3. At a data regenerating time, three beams a, b and c are irradiated onto the magnetooptic disk 1 from a three-beam magnetooptic head 5 to read three signals composed of a main signal d, subsignals e and f. The read three signals are transmitted to an adaptive type digital filter 8 so that crosstalk at the data regenerating time is removed from these signals. After this crosstalk has been removed from these signals, it is possible to detect a main signal d.sub.0 corresponding to a recording pit 4 of a data track as an object.
The crosstalk can be canceled by providing an optical pickup using three beams as shown in FIG. 1. However, in reality, high accuracy is required with respect to assembly of such an optical pickup and construction of electric circuits so that it is difficult to suitably assemble the optical pickup and construct the electric circuits. Further, cost of the optical pickup is increased so that no optical pickup can be practically used. Furthermore, in this case, there are problems about compatibility between the optical pickup and the general optical disk drive unit for recording data to only the land portion 2 or the groove portion 3. There are also problems about compatibility between the magnetooptic disk and the optical disk.
A memory capacity is gradually increased in a general apparatus for recording and regenerating optical information. Various kinds of recording systems are used to obtain a high density recording medium. For example, the recording systems are constructed by a system for reducing a wavelength of an LD (laser diode), a mark edge detecting system, a system for narrowing a track pitch (Tp) of the recording medium, etc. A drive unit using phase change (PC) media is recently manufactured as a product and technical advancement of this drive unit is expected. In one feature of the PC media, thermal conductivity is low and it is easy to control the size of a recording mark in comparison with magneto optical (MO) media. Accordingly, crosstalk can be restrained and the track pitch can be narrowed so that a land-groove recording system capable of most simply doubling a recording capacity is proposed. This land-groove recording system is disclosed as a "High Track Density Magnetooptical recording Using a Crosstalk Canceler" in Optical Data Strage '90. In such a land-groove recording system, the width of a land or groove generally playing the role of a guide groove is widened and data are also recorded to this groove by using three beams. Thus, two recording tracks can be formed at the narrow track pitch so that a high density record can be made.
The size of the recording mark can be easily controlled generally in the PC media so that crosstalk in a data section can be restrained by a general technique. However, a position information section such as a sector mark, an address, etc. not to be erased is recorded in advance by irregularities at a manufacturing time of the PC media. The position information section is called an ID section in the following description. No problems about the ID section can be solved since the ID section constitutes features of the PC media. In particular, existence or nonexistence of a mark is judged by existence or nonexistence of a groove of the PC media in the ID section of a pregroove format. However, a light spot reaches a groove portion in tracking of a land portion so that large crosstalk is caused by existence and nonexistence of a groove in an adjacent groove portion. Accordingly, no information of the PC media can be exactly detected.
The above system using three beams is used as a system for removing crosstalk in the land portion in the groove preformat ID section in the land-groove recording system. In this three-beam system, the three beams are adjusted to remove the crosstalk. However, in this three-beam system, it is necessary to arrange an adjusting mechanism which is very precise and special. Further, in this case, it is necessary to arrange laser diodes for emitting the three beams and a complicated circuit for separately detecting the three beams and making a calculation about these beams. As a result, problems are caused with respect to cost, durability, reliability, recording and regenerating efficiencies, a structural size. etc.